The Time Capsule cane used as a network drive. I've used one that way for a long time. Assume for a moment that your sidebar shows the Time Capsule. Double clicking it should open it just like any other hard drive. If you have set a password you will be asked for the password unless you have stored it in the keychain.

You might find this article helpful. It talks about the Airport Extreme but the same thing applies to the Time Capsule.